The phosphate coating is used as a pretreatment prior to painting, increasing corrosion protection, and providing for a better adhesion of the coating system.

When phos is used alone or in combination with oil (phos and oil) it lowers friction characteristics of sliding components or threaded parts. While typically called phos coating, phosphate alone has poor rust inhibiting characteristics and must be used in combination with oil or a top coat for corrosion protection. Zinc Phosphate can be applied to Ferric metals, but has no effect on Stainless Steel.

Phosphate Coating Characteristics
Color: dark gray / black
Typical Use: Anti –Galling/Basecoat
Top Coat: Oil or Paint

First to First Stud bolts for High Pressure Temperature Piping

REFERENCE
Stud bolts for pressure-temperature applications conform to the requirements of ANSI/ASME B16.5, Steel Pipe Flanges and Flanged Fittings.

LENGTH-FIRST TO FIRST
The length of stud bolt, measured parallel to the axis, is the distance from first thread to first thread. First thread is defined as the intersection of the major diameter of the thread with the base of the point. Please see the drawing above-this is confusing to most users!! Stud bolts are normally available in 1/4 inch length increments. Length tolerances, all stud bolt sizes, shall be as tabulated below:

Length, in. Length Tolerance, in.
to 12                           +/-0.062

over 12 to 18          +/-0.125

over 18                      +/-0.250

POINTS
Points shall be flat and chamfered, or sheared at option of the manufacturer. When points are flat and chamfered, the diameter of the flat shall not exceed the minor diameter of the thread, and shall be not less than one or more than two complete threads as measured from the extreme end parallel to the axis.

THREADS
Threads shall be Unified inch coarse thread series (UNC), Class 2A, for all stud bolt sizes 1 in. and smaller, and Unified inch 8 thread series (8 UN), Class 2A, for all stud bolts larger than 1 in., in accordance with ANSI/ASME B1.1. Acceptability of screw threads shall be determined based on ANSI/ASME B1.3.

MATERIAL
Chemical and mechanical requirements shall be specified by the purchaser and shall be in accordance with applicable ASME, ASTM, and ANSI codes and specifications current at the time of ordering.

DESIGNATION
It is recommended that stud bolts be designated in the following sequence: product name, nominal size, threads per inch, length, material, and protective finish, if required.

Example: ANSI/ASME B16.5 stud bolt,
5/8-11 x 3-1/2, ASTM A193, Grade B7, Zinc & Clear Chromate Plated

Tap End Stud

L Length – Measured end to end
T For 6B & 6BX studded flange connections with R, RX & BX gaskets, thread length maximum on end = 1 diameter + 1.5 pitch + 1/16-0
N Nut end thread length for 6B & 6BX studded flange connections with R, RX & BX gaskets shall be 2-1/2 diameters of full thread minimum.
* Class of Threads – Tap end threads may be furnished in any class thread specified. Nut end threads shall be American Standard Coarse or Fine series, Class 2A or 8 UN.

When ordering, please specify:
Diameter (D); Length (L); End-to-end dimension. (If length is figured first thread to first thread, order
must so specify.)
Tap end thread length (T) and thread series
Nut end thread length (N) and thread series

Double End or Tap End Studs are available in either rolled or cut threads. When the threads are rolled,
the full thread dimensions will increase slightly, and the diameter of the bodies will be undersized to the
pitch diameter of the thread.
Tap End Studs are available in ASTM A193 Grades of material or special materials. Sigma stocks the most
frequently used sizes of tap end studs in ASTM A193 Grade B7. Tap end studs can also be plated or
coated if allowances are made for coating thickness and thread fit.

Prints should be furnished on Double end or Tap End studs whenever possible.
** American Association of Wellhead Manufacturers -

TECHNICAL REPORT TR9501 Revision A

RECOMMENDATION FOR INTERCHANGEABLE STUD BOLTS AND TAP END STUDS FOR API SPEC 6A FLANGES

The ASTM F1428 specification as applied by Sigma Fasteners covers the corrosion-resistant coating system consisting of an inorganic aluminum particle-filled basecoat (SermaGard 1105) and an organic topcoat (SermaGard 1280 or Xylan 1014). The SermaGard basecoat is a water soluble slurry containing aluminum particles, a ceramic oxide pigment dispersed in a liquid binder of chromate/phosphate compounds. The organic topcoat consist of polymer and / or Fluoropolymer resins and pigments. At Sigma Fasteners these coatings are applied by conventional spray methods. The maximum service temperature of the coating system is 450° F (230° C). The coating system has a low susceptibility to inducing hydrogen embrittlement in steel parts of tensile strengths ≥ than 1000 MPa (≈RC31)

This coating system specification can be applied to alloy steels (ASTM A193 Grade B7),  ferritic and austenitic stainless steels (ASTM A193 GradeB8 and Grade B8M).

This coating system is in use in major offshore drilling, chemical and petrochemical facilities in the United States and worldwide.

SermaGard 1105 (ASTM F1428)

Sigma Fasteners is a licensed applicator for SermaGard products. 1105 is a ceramic-metallic sprayed
basecoat that at 1 mil of thickness or more affords 3000-4000 hours of ASTM B117 salt spray resistance,
with an appropriate topcoat. It can be used at high temperatures. It is extremely effective in salt
atmospheres. The SermaGard 1105 process involves curing at high temperatures (Minimum of 750 deg.
F) and subsequent burnishing with appropriate blast media to achieve conductivity. SermaGard 1105
contains aluminum flake.

SermaGard 1280

SermaGard 1280 is a fluorocarbon topcoat, which when applied to SermaGard 1105 basecoat gives
superior corrosion resistance and UV protection.

Sigma Fasteners manufactures and distributes a wide range of fasteners and bolting products – Fasteners for industry ranging from ½ through 4” and larger – In metric sizes M3 – M48 and larger. While Sigma is a full line distributor for all fastener products we specialize in custom bolts and custom bolting products for energy. Whether in emerging energy fields such as wind turbine bolting or legacy energy fields needing NACE certified MRO175 Sigma has the expertise to supply or custom manufacture all your bolting requirements. Our people have many years of experience in handling the most demanding expectations including the rigors North Slope of Alaska, to the regulatory hurdles of the South Texas Nuclear Project. Sigma Fasteners is ISO 9001:2001 certified and daily our associates deal with custom manufacturing many of the largest pressure and flow control equipment manufactures in the world. Sigma knows how to meet or exceed expectations of the most demanding fastener specifications in the industry. In addition, to distributing and manufacturing custom fasteners, Sigma also has fastener coating and fasteners plating capabilities that allow us control over your demanding needs.  Let Sigma be the answer to all your bolting needs.

The links below are from our standard fasteners catalog and includes items in stock and special order.

Nuts Bolts and Screws

Screws
Round Head Screws
Various Head Styles Machine Scerws
Tapping Screws (Approx. Hole Sizes)
Thumb and Wing Screws

B7 Studs and Nuts
Stud Bolts for Pressure-Temperature Piping
General Purpose End-to-End Studs
Tap End Stud Bolts
Double End Stud Bolts

Bolts
Hex Cap Screws (Finished Hex Bolts)
Wrench Openings for Square and Hex Bolts and Screws
Heavy Hex Bolts
Heavy Hex Structural Bolts
High-Strength Structural Bolting
Carriage Bolts and Lag Bolts
Square Bolts
Step Bolts and Countersunk Head Elevator Bolts

Nuts
Finished and Heavy Hex Nuts
Hexagon Machine Screw Nuts
Type A Forged Wing Nuts
Hex Slotted Nuts
Hex and Heavy Hex Jam Nuts
Hex Castle Nuts
Large Diameter Hexagon Head Cap Nuts
Round Spanner Nuts
Heavy Hex Nuts with Tommy Bar Holes

Sockets & Pins
Socket Head Cap Screws
Button Head and Flat Head Socket Cap Screws
Socket Set Screws
Hexagon Keys and Bits
Socket Head Shoulder Screws, Dowel Pins, and Slotted Set Screws
Square Head Set Screws and Socket Pipe Plugs
Physical Properties of Sockets
Point Terminology
Flange 12-Point Screws
Taper Pins
Threaded Taper Pins
Dowel Pins
Roll Pins
Cotter Pins

Washers
USS Wrought Washers
Stainless Steel Washers
S.A.E. Washers
Brass Washers
Beveled Washers
Spring Lock Washers
Tooth Lock Washers
Belleville Washers

Anchors
Wedge Anchors
Drop-In Anchors
Single Expansion Anchors
Machine Screw Anchors
Lag Shields
Lead Wood Screw Anchors
Hammer drive Anchors
Hollow Wall Anchors
Toggle Bolts
Toggle Wings and Nylon Nail Anchors
Plastic Anchors and Toggles

Locknuts
ESNA® Light Hex Nuts
FLEXLOC® Self-Locking Nuts
Prevailing-Torque Type Steel Hex and Hex Flange Nuts
ANCO Self-Locking Nuts

Self-Sealing Screws
Plated Carbon Steel
Stainless Steel
Plated Steel Self-Drilling

Self-Locking Fasteners

U-Bolts and Eye Bolts
Anchor Bolts & Bent Bolts
A-Bolts, Standard
U-Bolts, Long Tangent
Eyebolts-Regular Pattern
Eyebolts-Shoulder Pattern
Rod End Eyebolt Blanks

Metric Fasteners
Metric Hex, Head Cap Screws
Weights of Metric Hex Head Cap Screws
Metric Socket Cap Screws & Metric Flat Head Socket Caps
Metric Socket Set Screw & Metric Button Socket Caps
Metric Hex Nuts
Metric Flatwashers
Metric Internal & External Tooth Washers
Metric Lockwashers

Improve Make up and break out torque of bolts. Xylan is a fluoropolymer topcoat manufactured by Whitford Corporation, which in the 1014 and 1070 coatings afford high lubricity (co-efficient of friction as low as .02), and corrosion resistance of approximately 1000 hours(ASTM B117) when applied over phosphate, and up to 2000 hours when applied over electroplating. These are solvent based thin film topcoats. These Xylan products have a maximum temperature ranging up to 500 deg. F.  Xylan 1000 and 1400 series may also be applied over other basecoats, for added corrosion protection.  The 1400 series coatings by Whitford (typically 1424), are low voc coatings. They have a coefficient of friction of .05 to .10, and a maximum constant operating temperature of 400 deg. F. The corrosion resistance of the 1400 series is approximately 1500 hours, when applied over a suitable basecoat such as zinc electroplating.

Sermagard Coated Bolts

Sigma Fasteners is a licensed applicator for Sermagard products. 1105 is a ceramic-metallic sprayed basecoat that at 1 mil of thickness or more affords 3000-4000 hours of ASTM B117 salt spray resistance, with an appropriate topcoat. It can be used at high temperatures. It is extremely effective in salt atmospheres. The Sermagard 1105 process involves curing at high temperatures (Minimum of 750 deg. (F) and subsequent burnishing with appropriate blast media to achieve conductivity. Sermagard 1105 contains aluminum flake and Chromate. Sermagard 1280 is a fluorocarbon topcoat, which when applied to Sermagard 1105 basecoat gives superior corrosion resistance and UV protection.

Moly Coated Bolts

Molybdenum disulfide coated bolts are commonly used to improve the performance in extremes of load carrying capacity, operating temperature and coefficient of friction. This coating provides effective lubrication in a wide range of loads, in many cases exceeding 250,000 psi. Moly coatings lubricate sacrificially by transferring lubricant between the two mating surfaces, which helps to reduce both wear and the coefficient of friction. Moly coatings are a combination of molybdenum disulfide lubricant and high performance resins. The coating is thermally cured to bond thoroughly with the base metal of the coated part. Moly coated bolts can solve problems associated with corrosion, chemical exposure, and abrasion. offer excellent corrosion and chemical resistance and a barrier protection better than phosphate. With Moly’s exceptional barrier protection, it is appropriate for more severe environments and is often used in chemical processing and oil field equipment.

Teflon Coated Bolts

Over  seventy years ago a DuPont scientist, discovered polytetrafluoroethylene (PTFE) — a fluoropolymer that is corrosive chemical and heat resistance, and the world’s most slippery surface.  Teflon Coated Bolts have a Low Coefficient of Friction – The coefficient of friction of Teflon is generally in the range of 0.05 to 0.20, depending on the load, sliding speed, and particular Teflon coating used. Teflon Coated Bolts are Nonwetting – Since surfaces coated with Teflon are both oleophobic and hydrophobic, they are not readily wetted. Cleanup is easier and more thorough—in many cases, surfaces are self-cleaning. Teflon Coated Bolts are Heat Resistance – Teflon industrial coatings can operate continuously at temperatures up to 260°C/500°F.  Teflon Coated Bolts have Cryogenic Stability – Many Teflon industrial coatings withstand severe temperature extremes without loss of physical properties. Teflon industrial coatings may used at temperatures as low as -270°C/-454°F. Teflon Coated Bolts are Chemical Resistance – Teflon is normally unaffected by chemical environments. The only chemicals known to affect all Teflon industrial coatings are molten alkali metals and highly reactive fluorinating agents.

Coated Bolt Torque Chart

Duplex stainless has twice the yield strength of conventional austenitic stainless steels. Duplex stainless has high corrosion cracking resistance

Duplex Stainless Double End Studs

and high resistance to corrosion pitting as well as good general corrosion resistance in a wide variety of environments. Duplex stainless is the choice in extremely corrosive environments or were wear resistance and galling resistance is required. Many chemical environments not hospitable for standard 18-8 stainless is handled by Duplex stainless bolts. Duplex Stainless bolting handles nitric, hydrofluoric and phosphoric acids well at ambient temperatures. At elevated temperatures in chloride or sea water environments duplex stainless bolts have resistance to pitting and stress corrosion cracking superior to 316 stainless. Duplex stainless in various forms is used widely in heat exchangers, petroleum refining, offshore, petrochemical, pulp and paper industries.
Duplex stainless in typical Annealed condition has an ultimate tensile strength of 105 ksi.

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High Strength Super Alloy Bolts

17-4 is a precipitation hardening Stainless steel alloy. This chromium-nickel grade stainless steel has excellent mechanical strength. It corrosion resistance and high strength properties hold up very well in high temperature service up to 800 degrees F.  17-4 is used for high strength and elevated temperatures as well as in applications where high fatigue strength is required. 17-4 has good resistance to galling, seizing and stress corrosion. The corrosion resistance of 17-4 is superior to other chromium nickel stainless alloys.

17-4 Multiple Conditions available:

H 1100 – Tensile Strength 140 ksi

HH 1150 – Tensile Strength 135 ksi

13-8 Custom Bolts

13-8 is a precipitation hardening stainless steel. It is much like 17-4 in that it is a high strength stainless while possessing excellent corrosion resistance. 13-8 stainless alloy is used when good stress corrosion cracking resistance is required.

660 Custom Bolts

ASTM A453 660 Grade A,B or D a heat treated and age hardened version of A-286 is a popular high temperature precipitation hardened alloy. The high strength and oxidation resistance up to 1500 degrees F. 660 has excellent corrosion resistance up to 1300 degrees F and has fair salt spray corrosion resistance.

Material Selection Chart

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The ASME B16.5 – 1996 Pipe Flanges and Flange Fittings, flange bolt and gasket standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings.

The standard includes flanges with rating class designations 150, 300, 400, 600, 900, 1500, and 2500 in sizes NPS 1/2 through NPS 24, with requirements given in both metric and U.S units. The Standard is limited to flanges and flanged fittings made from cast or forged materials, and blind flanges and certain reducing flanges made from cast, forged, or plate materials. Included in this Standard are requirements and recommendations regarding flange bolting, flange gaskets, and flange joints. The standard covers the required number of bolts, diameter of the stud bolts, length of stud bolts and ring size in R, 1RF, RTJ, and RX  gaskets.

Flange Bolt Requirements

Download Torque Value Chart

Covering bolts on Wellhead Equipment, Valves and chokes, and loose flanged connectors.

*This chart is for general practice purposes only and should not be in the engineering or design of any products. The most current edition of the API specification may be obtained on the API Standards website to make sure you have the most current edition of API 6A. For most the accurate references in critical situations torque values should be replaced with field measured tension values. Accurate stud tension is difficult to attain using torque, because friction has a significant effect on the torque–tension relationship. Any thread damage (however minor), additional lubrication, or standard deviations within the range can change friction and thereby the expected outcome.